Electrode for electrolytic devices



Nov. 21, 1933. F. w. MCNAMARA 1,936,252

ELECTRODE FOR ELECTROLYTIC DEVICES Filed Aug. 15, 1930 INVENTOR.

`@Y @CQ ATTORNEYS.

?atented Nov. 2i, 1933 f ntuc'raonu non acupunctuur@ Frederick W. McNamara, North Adams, lll/laca,

assignorr to Sprague Specialties (Campen Quincy, itz/lass., a corporation of .lidassachtnettc Application August l5, o. @35,5931

t (Cl. llfnelil non-nlm-forming material forms the container El@ for the electrolyte.

The electrolyticcondenser is characterized by the fact that when an electric current is passed through it, a film is built up on the part of the anode immersed in the electrolyte," which i'llrn 'in possesses high dielectric capacity and high in;1

sulating properties, permitting only a Very slight current to pass from the anode toward the cathode. lThe dielectric capacity ci such a condenser is directly proportional to the area oi the anode covered by the film and thus directly proportional to the area oi' the anode immersed in the elec trolyte. ,To obtain highcapacity in a small 'volz ume it is therefore desirable to have this part o the anode with as large surface as possible.

i The passage of current through the condenser, however causes oxygen to be liberated at the anode, which attacks the anode at the gas=elecE trolyte inter-face. If the anode be constructed of thin sheet the result of this attack is that the anode becomes weakened and in a short time fails mechanically.

.The products Vof the attack, moreover, are substances which normally foul the electrolyte. To insurev a minimum of corrosion, the anode, at the point of projection from the electrolyte should be of as small surface as possible; and at the same time to insure strength, should be as sub= stantial as possible.

A desirable anode .is then one which combines the qualities of being of small surface at the point of projection from the electrolyte and of large surface where it is immersed in the electrolyte. In the prior art such construction has been attempted by making the anode of two pieces, one of which, a narrow stem, projects from the electrolyte and the other, consisting oi rolled or crimped foil, is totally immersed in the electrolyte. The two pieces are joined together at points which after assembly are immersed in the electrolyte. This joining is habitually performed by riveting, Welding, a combination of the two or other well-known means. Such construction is costly, involving as it does a multiplicity of operations. It is furthermore characteristic of such construction that adjacent to the joining points 1 ized by low insulating resistance and increase the or contacts are found seams, cracks, crevices and the like. In an electrolytic condenser incorporating such an anode the electrolyte has no free access to these seams and cracks and accumulation ci gas retards or prevents altogether the formation of the ln'l at such places. Thus, the nlm formed on the anode will be irregular and ci un certain properties in ythe neighborhood oi these seams and cracks. These places are character- 6d leakage current or the condenser. Furthermore, when such a condenser is in operation, slight vi1 bration or other moti ay disturb the accumulated gas, exposing a anodensurface tcelec= tric current. This may result in a possible short circuiting ot the condenser.

The prior types ci anodes alsosuffer from the fact that the ratio of edgesto surfaces is unnecessarily high. To build a smooth film it is necessary to have on the anode a fairly smooth metal 7g surface. This necessary smoothness is not to be obtained at a sharp edge or point and consequently poor films are formed in these regions. it is, moreover, characteristic of delectrics such as these films are, that when charged, the charge tends to be concentrated in the sharp edges or points. So that when anodes are constructed with sharp-edged foil a high concentration oi charge accumulates in these edges which frequently results in ilashovers, high leakage and the like.

Anodes Whicheliminate all of these diilculties have been proposed in the co-pending application, Ser. No. 416,939 led December 27, 1929, of F. Desmond Sprague and R. U. Clark, such anodes consisting o a thin walled corrugated tube provided With a narrow supporting neck.

In a preferred embodiment of' such anodes as also shown in the co-pending application Ser. No. 441,128 led April 2, 1930, of Max Knab, the tube is provided with helical corrugations. The area of such anodes and thus the capacity of the condenser depends on the mean diameter of the tube, the number of threads per inch and the depth of the thread. As the number of the depth of the im threads cannot be increased beyond certain limits, when such limits have been reached, the capacity of the condenser can only be increased by increasing the diameter of the tube.

To further increase the capacity of the con#- denser for a given container without sacrificing the advantages obtained with the above described anodes, I have devised a multiple-piece anode consisting of a plurality of concentric corrugated tubes of diferent diameters, each provided with vices consisting oi." concentric corrugated tu' es.

ifi. ther object oi niv invention is to provide a pe: e 'f' riechanical and electrical Contact lse= tv'eel ier object oi invention is such a mechanical ele means oi cooperating extensions of ual pieces, these extensions proies elec. lyte.

Fu her objects my invention as this suecidcation progresses Rete a' non" to drawing, wl part o. this specification, the 'ligure elevation, pa'" awe: sho

an electrolytlc condenser embody le tion. The condenser coin'or a 2o, which may be oi film-romains or houille -iorn ng material an anode which consists of outer piece l an inner piece 2. The outer piece l comprises two f hollow supportil 3 'od a yalled tubular por tl ov conical ed with circulating holes 6. he supporting neclz Ei is bevelled. tabulag eierablv provided with closely spaced helical corrugations, although other types oi corrugations may be pro vided or even a smooth tubular portion used.

inner piece 2 consists oi a tubular portion. 8 and slig` tlv tapered supporting neclt lo, the tube d and noch lil being connected by means a conical portion n' the portion 9 is provided Jv with circulating holes 9a. The tube d which is n il tl being inter-connecte .c d prov d yoi. smaller diameter than the tube s is concentricallf located within the latter, whereby the supporting necli; lo is surrounded by and project-- ing through the supporting neclr 3. The free of the neck lo is threaded at ll and is provided with nuts lZ--lZ to forni the outside oi the anode.

The tubular portion s ls preferably provided with closely spaced flat helical corrugations, although other types of corrugations may be pron vided or even a smooth tubular portion used.

.A suitable electrolyte 13 is provided in the container, which fully covers the conical portion 5 of the outer tube.

The container l is provided with a cover la of insulating material which rests in an annular indentation l5 oi the container and which by means of the lower nut l2 supports the anodes 1 and 2. On its top, the cover is provided with a peripheral recess in which rests a rubber gasket 17 over which the free end of the container is crimped for the proper sealing oi' the device. Sealing means (not shown) also may bc provided between the cover 14 and the neck l0 of the anode.

A rubber vent 18 with a for the escape of the gases.

To prevent corrision between the two pieces of the anode as well as other objectionable effects, for instance undue contact resistance and thus pin hole 19 provides other, each cocasse maintain the advantages oi' a one-piece anode of the type disclosed in the above applications, special care is to be taken torinsure perfect electrical and mechanical connection between the Jo pieces l and 2 of the anode. This, I have obtained by providing a forced fit between the supporting neclrs lo and 3.

While 'lave described and illustrated an g of only two pieces, it is well i'stood 'amt such anodes may comprise a oi pieces similarly arranged. It without departing from the spirit ion to arrange the tubular portions portions asvmmetricaily instead of l secure by heitere Patent is:

l. in anode for electron/tic condensers comprising a plurality oi pieces located within each ece having two integral portions, one being a thin walled tubular portion having erimps in planes substantially perpendicular to the4 or the tube, the other portion being of 105 substantial thickness and of small surface, the l'tions of small surface of the individual pieces bei g in irimate electrical and mechanical contact with each other.

.ln an electrolytic device, a container, an ectrolyte and an anode comprising a plurality or substantially concentric pieces, each piece hav L; portion forming a corrugated tube of closely spaced flat helical corrugations submerged in the electrolyte and a portion emerging from "ce electrolyte, said emerging portions of the individual pieces forming an intimate electrical mechanical Contact with each other.

ln an electrolytic condenser, a container, an electrolyte and a multiple piece electrode, each piece oi said electrode comprising a tubular corrugated portion immersed in the electrolyte and a cof-axial portion extending from the electrolyte, the portions extending lfrom the electrolyte of the individual pieces being in direct and intimate electrical and mechanical connection with each other.

ln an electrolytic condenser, a cylindrical container forming one electrode of the condenser and a second electrode comprising tubular members mechanically and electrically connected with each other, said members being disposed substantially co-,axlal with said container and having neck portions surrounding each other.

5. An electrode for electrolytic devices comprising a tubular member provided with an attenuated neck and a second tubular member disposed withln said rst member and having a. portion snugly fitting in said attenuated neck and projecting therethrough, to form an outside con- 'nection for the electrode.

6. ln an electrolytlc device comprising a container forming one electrode, a cover of insu-` lating material, a second electrode comprising a plurality oi individual members co-axlally disposed within said container, one o! said members projecting through said cover to form an outside terminal for said electrode and a. second o!- said members intimately surrounding said first member.

iooeoyaea one ioiiimng 'tlie eiective electrode and tlie other connecting said electrode to an outside terminal, the latter portions of tlie individual members surrounding each other and being in direct and intimate electrical and mechanical contact with each other.

9. electrode :for electrolytic condensers comprising a tubular member having an attenuated neck, and a second tubular member disposed Within said first member and being with said neck in intimate electrical connection.

MEDERCK W. MCNAi/ARA.

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